Purge and trap concentrator with sparge vessel

ABSTRACT

A purge and trap concentrator system that includes a sparge vessel, and includes a variable gas flow valve for controlling the gas pressure in an analytic trap or the sparge vessel; a sensor that detects both a foaming sample state and a high liquid level in the sparge vessel, using one optical sensor; a control scheme that re-directs the purge gases to a second inlet of the sparge vessel during a foaming condition; a control scheme that uses a split flow to enhance the quantity of sample gases passed from an analytic trap; an electrically powered thermal energy source with a fan raising the sparge vessel temperature via thermal convection.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of application Ser. No.12/037,977, titled “PURGE AND TRAP CONCENTRATOR WITH SPARGE VESSEL,”filed on Feb. 27, 2008, which is now U.S. Pat. No. 7,803,635.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to purge and trap concentrator systems,and, more particularly, to those that include a sparge vessel. Theinvention, in various embodiments, includes: (1) a variable gas flowvalve for controlling the gas pressure in the sparge vessel, or in ananalytic trap; (2) a foam sensor subassembly that detects both a foamingsample state and a high liquid level in the sparge vessel, using asingle optical sensor; (3) a control scheme in which a purge andsampling procedure can continue after a foaming sample has beendetected, by re-directing the purge gases to a second inlet of thesparge vessel; (4) a control scheme in which a desorbtion mode uses asplit flow to enhance the quantity of sample gases that are passed to ananalyzer instrument from an analytic trap; (5) a thermal heatersubassembly that uses an electrically powered thermal energy source anda fan to raise the temperature of the sparge vessel via thermalconvection during a bake mode, by directing heated air to the spargevessel using a ductwork arrangement with the fan; and (6) a desorbtionpressure control mode in which the pressure at an analytic trap isbrought to a controlled value that will allow the system to jump to theinject mode without undergoing a pressure surge at the trap.

2. Description of the Related Art

Purge and trap concentrators have been is used to extract VOCs fromaqueous samples, or from a solid sample matrix. In many systems, asample is housed in a sealed vessel known as a sparge vessel. The spargevessel typically is constructed in a U-shape design with an inlet side(purge portion) and an outlet side (sample portion). An inert gas (purgegas) of helium or nitrogen sweeps the aqueous sample at a controlledflow rate known as purging. The purge gas is introduced on the purgeportion of the sparge vessel; typically the purge gas stream passesthrough a frit placed in the bottom of the sample portion of the spargevessel. The frit disperses the gas into many fine streams to increasesurface contact of the gas with the sample for extraction of VOCs. Oneproblem with purging aqueous samples is they have a tendency to foam,and if the foam is left unattended the sample could come in contact withinternal pathway components of the instruments pathway causingcontamination to the entire system. This can require costly repairs anddowntime for the testing laboratory, along with rendering the analyticaltest data invalid.

Today most purge and trap concentrators have a foam detection sensorthat will turn off the purge gas and stop the sampling process, orcontinue in a “safe mode” to prevent costly repairs. The problem here isthat the sample is then wasted and deemed unusable. The laboratory willhave to re-run the sample (if it has one) or contact the client to senda new sample.

One approach to this problem is pre-treating suspect samples with ananti-foaming agent, such as Dow Corning Silicone RID emulsion. Howeverthis treatment can raise concerns regarding the sample integrity. Asecond approach is to disrupt the foam with a heat source to continuethe analysis. However the heating of the foam and headspace of thesample containing extracted VOCs could also raise some questions on theintegrity of the extracted VOCs.

Most purge and trap concentrators using a sparge vessel provide an inert(purge) gas that is swept through the concentrated chemical sample at acontrolled flow rate, thereby extracting the VOCs from the sample. Theextracted VOCs are then placed in fluidic communication with anadsorbent trap for concentrating. The adsorbent trap is thermally heatedto release the extracted VOCs from the adsorbent bed of the trap. Asecond passage of inert (carrier) gas is in fluidic communication withthe adsorbent trap to back-flush the VOCs from the adsorbent trap to ananalytical device know as a Gas Chromatograph (GC) for separation andidentification.

Conventional purge and trap concentrators typically contain a switchingdevice for the purpose of networking the fluidic communication of purgegas and carrier gas to the adsorbent trap during the desorbtion step.The gas chromatograph typically controls the carrier gas flow rate, asthe purge and trap concentrator controls the purge gas flow rate. Thepressure and flow rates for the purge and carrier gas usually differ,causing some dead volume issues during the switching of fluidiccommunication of purge gas pathway to the carrier gas pathway during thedesorbtion step. The dead volume can affect the transfer rate andanalytical resolution of the extracted VOCs. When sampling an aqueoussample matrix, depending on the carrier gas flow settings and purge andtrap desorbtion settings, an unwanted amount of moisture content issometimes transferred to the gas chromatograph, which affects analyticalresolution and detected recovery of the extracted VOCs.

Conventional purge and trap concentrators using a sparge vessel areoften used to extract VOCs, typically from an aqueous or a solid samplematrix. The purge and trap concentrators typically consist of threestages for a completed sample analysis cycle: (1) a purge step, (2) atrap desorbtion step, and (3) a bake step. The bake step is a system“cleanup” step used for preparing the system to receive consecutiveconcentrated samples for analysis. Typically a gas flow is in fluidiccommunication with the adsorbent trap and the sparge vessel for thepurpose of preparing the sample pathway for the next sample analysis.This gas flow typically sweeps the entire sample pathway, whileconcurrently thermally heating the adsorbent trap to a setpointtemperature higher than the desorbtion setpoint temperature, for thepurpose of removing contaminates from the trap in preparation of nextsample analysis. If the purge and trap concentrator is connected to avial auto sampler, such as an EST Analytical Centurion™ Vial AutoSampler, a heated rinsing liquid (typically deionized water) is flushedthrough the sparge vessel for cleaning the sparge vessel of unwantedcontaminates, concurrent with the bake step. A low amount of carryoverof unwanted contaminates sometimes will exist, even in today's purge andtrap concentrators.

An improved purge and trap concentrator is needed to detect and preventfoaming without questioning the integrity of the extracted VOCs, toprovide a method for removing the remaining contaminates from thesampling pathway that could affect the reporting of analytical data fromthe subsequent sample analysis, and a method for providing appropriatesampling process parameters to improve overall analytical analysis ofextracted VOCs.

SUMMARY OF THE INVENTION

Accordingly, it is an advantage of the present invention to provide anapparatus and method of sampling which delivers a vapor sample to ananalyzer instrument using a Desorbtion Mode that has a “split flow”characteristic, which allows a greater volume of gas to be delivered tothe analyzer instrument using an arrangement that does not increase theamount of water that is delivered to the analyzer instrument.

It is another advantage of the present invention to provide an apparatusand method of operation that minimizes the amount of time between a bakestep at the end of a first sampling cycle and a purge step at thebeginning of the next sampling cycle, by using a fan that cools thesparge vessel by thermal convection.

It is yet another advantage of the present invention to provide anapparatus and method of sampling that uses a thermal convection heaterfor heating a sparge vessel.

It is still another advantage of the present invention to provide anapparatus and method of sampling using a sparge vessel, in which asingle sensor is provided that can detect both foaming and an overfillcondition.

It is a further advantage of the present invention to provide anapparatus and method of sampling that provides a foam sensor in a spargevessel, and upon detecting foaming, creates an alternative route for thepurge gas that can bypass the frit of the sparge vessel and allow thepurge cycle to continue without aborting.

Additional advantages and other novel features of the invention will beset forth in part in the description that follows and in part willbecome apparent to those skilled in the art upon examination of thefollowing or may be learned with the practice of the invention.

To achieve the foregoing and other advantages, and in accordance withone aspect of the present invention, a purge and trap concentratorsystem is provided, which comprises: a (a) a system controller; (b) asource of gas, which provides a first gas; (c) a plurality of fluidiccontrol devices and a plurality of fluidic passages which fluidicallyconnect the plurality of fluidic control devices; (d) a gas flow controlvalve that is controlled by a signal from the system controller, the gasflow control valve having a first fluidic inlet and a first fluidicoutlet which, under control of the signal, acts to pass a gas flowtherethrough, the first fluidic inlet being in fluidic communicationwith the source of gas and receiving the first gas, the first fluidicoutlet dispensing a second gas when required by the signal; and (e) ananalytic trap, having: (i) a second fluidic inlet, a third fluidicinlet, and a second fluidic outlet; wherein: (A) the second fluidicinlet is in fluidic communication with the first fluidic outlet of thegas flow control valve, (B) the third fluidic inlet is in fluidiccommunication with a third outlet of an external instrument, and (C) thesecond fluidic outlet is in fluidic communication with a fourth inlet ofthe external instrument; (ii) a first chamber that is coupled to thethird fluidic inlet, the first chamber having previously received aconcentrated chemical sample, the first chamber acting to remove atleast one predetermined substance from the concentrated chemical sample,thereby creating a third “extracted sample” gas flow; and (iii) a secondchamber that is coupled to the first chamber, to the second fluidicinlet, and to the second fluidic outlet, the second chamber beingconfigured to receive: (A) the third extracted sample gas from the firstchamber, and (B) the second gas from the first fluidic outlet of the gasflow control valve by way of the second fluidic inlet; (f) whereinduring a desorbtion procedure: (i) the second gas is received at thesecond fluidic inlet of the analytic trap, (ii) a fourth gas is receivedat the third fluidic inlet of the analytic trap from the third outlet ofthe external instrument; and (iii) at the second chamber the second gasis combined with the third extracted sample gas, thereby creating alarger overall fifth gas flow that now becomes available for analysis bythe external instrument.

In accordance with another aspect of the present invention, ananalytical chemical sampling apparatus is provided, which comprises: asystem controller; a source of inlet gas; a sparge vessel having a purgeportion and a sample portion, the purge portion of the sparge vesselreceiving inlet gas from the source of inlet gas during a samplingprocedure, the sparge vessel being used to house a chemical sample inthe sample portion during the sampling procedure, which allows volatilegases to be removed from the chemical sample and directed through atleast one fluidic outlet pathway; a source of thermal energy that isproximal to, but spaced-apart from, the sample portion of the spargevessel; a fan; a temperature sensor located proximal to the sampleportion of the sparge vessel, the temperature sensor outputting a firstsignal to the system controller; a ductwork subassembly that (a)contains the source of thermal energy, (b) receives a first air flowfrom the fan, (c) directs the first air flow toward the source ofthermal energy, thereby creating a second air flow having an increasedtemperature during a bake procedure, and (d) directs the second air flowtoward the sample portion of the sparge vessel during the bakeprocedure, thereby heating the sample portion of the sparge vessel byuse of thermal convection; wherein the system controller is configuredto control a bake temperature during the bake procedure, while cleaningthe sample portion of the sparge vessel, by using the temperaturesensor's first signal to determine a present temperature near the spargevessel, and by controlling the fan and the source of thermal energy soas to raise the temperature of the second air flow.

In accordance with yet another aspect of the present invention, ananalytical chemical sampling apparatus is provided, which comprises: (a)a system controller; (b) a source of gas, which provides a first gas;(c) a gas flow control valve that is controlled by a first signal outputby the system controller, the gas flow control valve having a firstfluidic inlet and a first fluidic outlet which, under control of thefirst signal, acts to pass a gas flow therethrough, the first fluidicinlet being in fluidic communication with the source of gas andreceiving the first gas, the first fluidic outlet dispensing a secondgas when required by the first signal; (d) a plurality of fluidiccontrol devices and a plurality of fluidic passages which fluidicallyconnect the plurality of fluidic control devices, the second gas beingdirected into the plurality of fluidic control devices and a pluralityof fluidic passages; and (e) a sparge vessel having a purge portion anda sample portion, (i) the purge portion of the sparge vessel having asecond inlet that, during a sampling procedure, receives the second gasfrom the gas flow control valve, through the plurality of fluidiccontrol devices and a plurality of fluidic passages; (ii) the sampleportion of the sparge vessel being used to house a chemical sampleduring the sampling procedure, which allows volatile gases to be removedfrom the chemical sample and directed from the sparge vessel sampleportion through a second fluidic outlet; (iii) the sample portion of thesparge vessel including a foam sensor that determines whether thechemical sample undergoes foaming; and (iv) the sample portion of thesparge vessel having a third inlet that, if the chemical sampleundergoes foaming to an extent that the foaming is detected by the foamsensor, then under the control of a second signal output by the systemcontroller, the plurality of fluidic control devices and a plurality offluidic passages change state and re-direct the second gas such that ittravels to the third inlet instead of to the second inlet, therebyallowing the sampling procedure to continue during a foaming state whiletemporarily bypassing the purge portion of the sparge vessel.

In accordance with still another aspect of the present invention, ananalytical chemical sampling apparatus is provided, which comprises: (a)a system controller; (b) a source of gas, which provides a first gas;(c) a gas flow control valve that is controlled by a first signal outputby the system controller, the gas flow control valve having a firstfluidic inlet and a first fluidic outlet which, under control of thefirst signal, acts to pass a gas flow therethrough, the first fluidicinlet being in fluidic communication with the source of gas andreceiving the first gas, the first fluidic outlet dispensing a secondgas when required by the first signal; (d) a plurality of fluidiccontrol devices and a plurality of fluidic passages which fluidicallyconnect the plurality of fluidic control devices, the second gas beingdirected into the plurality of fluidic control devices and a pluralityof fluidic passages; (e) a sparge vessel having a purge portion and asample portion, (i) the purge portion of the sparge vessel having asecond inlet that, during a sampling procedure, receives the second gasfrom the a gas flow control valve, through the plurality of fluidiccontrol devices and a plurality of fluidic passages; and (ii) the sampleportion of the sparge vessel being used to house a chemical sampleduring the sampling procedure, which allows volatile gases to be removedfrom the chemical sample and directed from the sparge vessel sampleportion through a second fluidic outlet; and (f) a sensing subassemblypositioned within the sample portion of the sparge vessel at a levelabove a normal liquid level of the chemical sample, wherein the sensingsubassembly comprises: (i) an optical waveguide having a termination endthat emits an electromagnetic energy signal at a predeterminedwavelength; and (ii) a separate optical sensor that detects theelectromagnetic energy signal at the predetermined wavelength, theoptical sensor being spaced-apart from the optical waveguide terminationend; (g) wherein: (i) if the chemical sample is not exhibiting foaming,and is not exhibiting a high liquid level within the sparge vessel, thenthe optical sensor receives a substantially steady magnitude of theelectromagnetic energy signal at the predetermined wavelength, and thesystem controller operates normally; (ii) if the chemical sample isexhibiting foaming, then bubbles created by the foaming state tend tointerfere with the electromagnetic energy signal, and the optical sensordoes not receive a substantially steady magnitude of the electromagneticenergy signal at the predetermined wavelength, and the system controllerdetermines that is should begin operating in an alternative mode; and(iii) if the chemical sample exhibits a high liquid level within thesparge vessel, then the high liquid level tends to interfere with theelectromagnetic energy signal, and the optical sensor does not receive asubstantially steady magnitude of the electromagnetic energy signal atthe predetermined wavelength, and the system controller determines thatis should begin operating in the alternative mode; and (iv) the systemcontroller thereby is able to detect both a foaming condition and a highliquid level state using a single optical sensor.

In accordance with a further aspect of the present invention, a methodfor operating a purge and trap concentrator system is provided, in whichthe method comprises the following steps: (a) providing a systemcontroller, a gas source that supplies a first gas flow, a plurality offluidic control devices and a plurality of fluidic passages whichfluidically connect the plurality of fluidic control devices, ananalytic trap, a first fluidic inlet that is in communication with anexternal analyzer instrument, and a first fluidic outlet that is incommunication with the external analyzer instrument; (b) receiving asecond gas flow from the external analyzer instrument, through the firstfluidic inlet; (c) placing a concentrated chemical sample into a firstchamber of the analytic trap, directing the second gas flow into a firstend of the first chamber and removing at least one predeterminedsubstance from the concentrated chemical sample, thereby creating an“extracted sample” gas flow that is directed to a second end of thefirst chamber; and (d) receiving, at a second chamber of the analytictrap, the extracted sample gas flow from the first chamber; receiving,at a second inlet of the second chamber of the analytic trap, the firstgas flow from the gas source; and combining the first gas flow and theextracted sample gas flow at the second chamber and to create anenhanced gas flow that is directed through a second outlet of the secondchamber and further to the first fluidic outlet, and to the externalanalyzer instrument, thereby providing a larger overall enhanced gasflow that now becomes available for analysis by the external analyzerinstrument.

In accordance with a yet further aspect of the present invention, amethod for operating an analytical chemical sampling apparatus isprovided, in which the method comprises the following steps: (a)providing a system controller, a gas source that supplies a first gasflow, a plurality of fluidic control devices and a plurality of fluidicpassages which fluidically connect the plurality of fluidic controldevices, a sparge vessel having a purge portion and a sample portion;(b) placing a chemical sample into the sample portion of the spargevessel, and during a sampling procedure, receiving the first gas flow ata first inlet at the purge portion of the sparge vessel, therebyremoving volatile gases from the chemical sample and directing thevolatile gases past a foam sensor and to a first fluidic outlet wherethe volatile gases leave the sparge vessel; and (c) if the chemicalsample undergoes foaming to an extent that the foaming is detected bythe foam sensor, then, under the control of the system controller,changing a state of the plurality of fluidic control devices and aplurality of fluidic passages to re-direct the first gas flow such thatit instead travels to a second inlet at the sample portion of the spargevessel, thereby allowing the sampling procedure to continue during afoaming state while temporarily bypassing the purge portion of thesparge vessel.

In accordance with a yet further aspect of the present invention, apurge and trap concentrator system is provided, which comprises: (a) asystem controller; (b) a first source of gas, which provides a firstgas; (c) a plurality of fluidic control devices and a plurality offluidic passages which fluidically connect the plurality of fluidiccontrol devices; (d) a variable flow rate gas flow control valve that iscontrolled by a first signal from the system controller, the gas flowcontrol valve having a first fluidic inlet and a first fluidic outletwhich, under control of the first signal, acts to pass a gas flowtherethrough, the first fluidic inlet being in fluidic communicationwith the source of gas and receiving the first gas, the first fluidicoutlet dispensing a second gas when required by the first signal; (e) anexternal instrument, which includes second source of gas that supplies athird gas, the external instrument having a second fluidic outlet thatsupplies the third gas, and a second fluidic inlet; and (f) an analytictrap, having: (i) a first trap port, a second trap port, and a thirdtrap port; wherein: (A) the first trap port is selectively in fluidiccommunication with the first fluidic outlet of the gas flow controlvalve, (B) the second trap port is selectively in fluidic communicationwith a vent, through the plurality of fluidic control devices andplurality of fluidic passages, and is selectively in fluidiccommunication with the second fluidic output of the external instrument,through the plurality of fluidic control devices and plurality offluidic passages, and (C) the third trap port is selectively in fluidiccommunication with the second inlet of the external instrument; (ii) afirst chamber that is coupled to the second trap port, the first chamberbeing designed to receive a concentrated chemical sample, the firstchamber acting to remove at least one predetermined substance from theconcentrated chemical sample, and thereby create an “extracted samplegas flow”; (iii) a second chamber that is coupled to the first chamber,to the first trap port, and to the third trap port; and (iv) a trapheater; (g) wherein, before a desorbtion procedure begins: (i) theplurality of fluidic control devices are in a first state; (ii) thesecond gas is received at the first trap port of the analytic trap, andflows into the first chamber; (ii) a fourth gas exits the first chamberat the second trap port, and flows toward a vent, through the pluralityof fluidic control devices and plurality of fluidic passages, includinga vent valve that is open at this time; (iii) then the vent valve isclosed by a second signal from the system controller, and the fourth gasbegins to build a desorbtion pressure control (“DPC”) pressure at thesecond trap port, wherein the DPC pressure is controlled by the gas flowcontrol valve, which is controlled by the first signal from the systemcontroller; and (iv) the DPC pressure reaches a predetermined magnitude;and (h) wherein, a desorbtion procedure begins, such that: (i) theplurality of fluidic control devices are activated into a second state,under the control of a third signal from the system controller; (ii) thethird gas from the second outlet of the external instrument now flows tothe second trap port and into the first chamber; (iii) the extractedsample gas flow travels from the first chamber into the second chamber;and (iv) a fifth gas flow, which includes the extracted sample gas flow,exits the second chamber at the third trap port and flows toward thesecond inlet of the external instrument, through the plurality offluidic control devices and plurality of fluidic passages.

Still other advantages of the present invention will become apparent tothose skilled in this art from the following description and drawingswherein there is described and shown a preferred embodiment of thisinvention in one of the best modes contemplated for carrying out theinvention. As will be realized, the invention is capable of otherdifferent embodiments, and its several details are capable ofmodification in various, obvious aspects all without departing from theinvention. Accordingly, the drawings and descriptions will be regardedas illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of at least one embodiment of the invention taken inconjunction with the accompanying drawings. The accompanying drawingsincorporated in and forming a part of the specification illustrateseveral aspects of the present invention, and together with thedescription and claims serve to explain the principles of the invention.In the drawings:

FIG. 1A is a fluidic schematic diagram of a purge and trap concentratorsystem constructed according to the principles of the present invention,showing the system in an operating mode called “Purge Mode A.”

FIG. 1B is a fluidic schematic diagram of the purge and trapconcentrator system of FIG. 1A, showing the system in an operating modecalled “Purge Mode B.”

FIG. 2 is a fluidic schematic diagram of the purge and trap concentratorsystem of FIG. 1A, showing the system in an operating mode called“Standby—Dry Purge Mode.”

FIG. 3 is a fluidic schematic diagram of the purge and trap concentratorsystem of FIG. 1A, showing the system in an operating mode called“Desorb Mode—No Split.”

FIG. 4 is a fluidic schematic diagram of the purge and trap concentratorsystem of FIG. 1A, showing the system in an operating mode called“Desorb Mode—With Split.”

FIG. 5 is a fluidic schematic diagram of the purge and trap concentratorsystem of FIG. 1A, showing the system in an operating mode called “BakeMode.”

FIG. 6 is a flow chart showing some of the logical steps used forcontrolling some of the various operating modes of the presentinvention, including the initial operating modes for “Standby” and“Purge Ready.”

FIG. 7 is a second flow chart showing some of the logical steps used forcontrolling some of the operating modes of the present invention,including the “Purge” mode.

FIG. 8 is a third flow chart showing some of the logical steps used forcontrolling some of the operating modes of the present invention,including the “Dry Purge” mode.

FIG. 9 is a fourth flow chart showing some of the logical steps used forcontrolling some of the operating modes of the present invention,including the “Desorb Ready” and the beginning of the “Desorb” mode.

FIG. 10 is a fifth flow chart showing some of the logical steps used forcontrolling some of the operating modes of the present invention,including the “Bake” mode.

FIG. 11 is a perspective view of a portion of the purge and trapconcentrator system of the present invention, showing the sparge vesseland the temperature control system used with the sparge vessel thatheats and cools the sparge vessel, under control of a system heatingcontroller.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the present preferred embodimentof the invention, an example of which is illustrated in the accompanyingdrawings, wherein like numerals indicate the same elements throughoutthe views. The exemplification(s) set out herein illustrate(s) at leastone preferred embodiment of the invention, in at least one form, andsuch exemplification(s) (is)(are) not to be construed as limiting thescope of the invention in any manner.

The terms “first” and “second” preceding an element name, e.g., firstinlet, second inlet, etc., are used for identification purposes todistinguish between similar or related elements, results or concepts,and are not intended to necessarily imply order, nor are the terms“first” and “second” intended to preclude the inclusion of additionalsimilar or related elements, results or concepts, unless otherwiseindicated.

Referring now to FIG. 1A, a fluidic schematic diagram is provided,generally designated by the reference numeral 10, for a first purgemode, in which a VOC (volatile organic compound) sample is extractedfrom an aqueous sample contained in a sparge vessel 20. Severaldifferent fluidic diagrams are provided herewith, and they all generallycontain the same hardware, but are configured in different arrangements.This description will start by introducing the hardware.

The fluidic diagram 10 includes five different solenoid valves, whichare either two-way or three-way valves, designated 151, 152, 153, 154,155, and 156 (or V1, V2, V3, V4, V5, and V6). There is also aneight-port (four-way) valve 140, in which some of its passageways can berepositioned by rotating or otherwise actuating the valve 140. There isa proportional flow control valve 100 (also referred as PV1) thatgenerally receives helium gas from an input source of helium gas at 50,and there is a vent to atmosphere at 102. There is a fluidic inlet at 82that receives carrier gas from an analyzer instrument 80, in generalwhich will be referred to as a gas chromatograph (or “GC”) for thisdescription of the present invention. There is also a fluidic outlet 84that sends gas samples to the same GC analysis instrument 80.

The various solenoid valves in the system 10 are also referred to bynames, as follows: V1 at 151 is referred to as the “Needle Valve;” V2 at152 is referred to as the “Dry Purge Valve;” V3 at 153 is referred to asthe “Vent Valve;” V4 at 154 is referred to as the “Backflush” or simply“Flush” valve; V5 at 155 is referred to as the “Drain Valve;” and V6 at156 is referred to as the “Bake Valve.” These valves will be energizedor de-energized as required by the system controller, for the variousmodes of operation of the system 10. Drain Valve V5 is used to drain thesparge vessel 20, at appropriate times during the processing cycles ofthe purge and trap analytical instrument 10. The valves in system 10 aresometimes referred to herein as a “plurality of fluidic controldevices;” the passageways between the valves are sometimes referred toherein as a “plurality of fluidic passages.”

It will be understood that the valves V1-V6 and the four-way valve 140can comprise virtually any type of automatically-controlled valves,including solenoids that are actuated by electrical signals. Variouscontrol valves are also available that can be actuated by hydraulic orpneumatic signals, for example, which could be used in the presentinvention, in combination with, or in lieu of, theelectrically-controlled solenoids described herein and in the drawings.Moreover, the control techniques could use either “analog” or “digital”control signals, and the automatically-controlled valves could then beeither “on-off” digital control valves, or proportional analog controlvalves, for example. Of course, in the illustrated embodiment,digitally-actuated solenoid valves are used. The variousautomatically-controlled valves used in the present invention generallyare used to allow vapors or liquids to pass therethrough (or to blockthem from doing so), and thus are generally referred to as “fluidicvalves.”

The proportional flow control valve 100 (PV1) is also referred to hereinas a “gas flow control valve” and also as a “pressure control valve.”Valve 100 has a fluidic inlet that receives source gas from the gasinput passageway 50, and valve 100 has a fluidic outlet that sometimeshas an “output gas” passing therethrough. Whether or not gas passedthrough the fluidic outlet depends on the control signal (at 108)received by the valve 100. Since valve 100 is a variable operatingdevice, the gas flow at its outlet can be 100% of the gas flow at itsinlet, thereby allowing a maximum pressure to be achieved downstreamfrom valve 100. On the other hand, valve 100 can be controlled to allowonly a fraction (or zero) of the inlet gas to pass therethrough to itsoutlet. Valve 100 typically operates as a pressure control valve, andmost of its operations (as discussed below) will be based on controllingits outlet pressure, and its system controller 110 (discussed below)typically controls from a programmable pressure setpoint that acts asthe process control variable. The setpoint value changes, depending onwhich operating mode is currently being used.

The fluidic diagram 10 includes a sparge vessel 20 that has two majorportions or “sides” which create a generally U-shaped appearance. Thesparge vessel can be filled with a liquid, such as distilled ordeionized water or other liquid of interest, and receives neutral gaseson the “input” side, and has a heater that will tend to heat up (andlater cool off) the “output” or “sample” side. This “sample portion” isgenerally indicated at the reference numeral 28 (see FIG. 11), which iswhere the sample to be analyzed is placed. A first inlet on the inputside of the sparge vessel is indicated at reference numeral 22, while asecond inlet at 24 is located near the outlet (or output) side of thesparge vessel. There is also a shut-off valve at 150 near this secondinlet 24. The outlet passageway for the sparge vessel is at referencenumeral 26.

The sparge vessel 20 receives some type of pressurized gas along eithera pipe or tube 42 or 40, and these pipes/tubes are connected to either aNeedle Valve 151 (V1) or a Dry Purge Valve 152 (V2). In general, theflow of gases starts at a helium input source through its inlet tubingor piping at 50, through the proportional flow valve 100 (PV1), througha T connection 138, through a second T connection 136, through a flowrestrictor 120, through the Needle Valve 151, and finally through theDry Purge Valve 152. This gas arrives at the inlet of the sparge vesselat 22, and then passes into the “sample portion” 28 of the sparge vessel20.

Within the sparge vessel itself is a frit 30 that disperses the gas intomany fine streams to increase surface contact of the gas with the samplefor extraction of volatile gases (e.g., VOCs). An enlarged portion (the“foam bubble” portion) of the sparge vessel glassware is at 32, wheresamples have a tendency to foam. Sparge vessel 20 has a sensingsubassembly at 34 which comprises a fiber optic cable 36 and an opticalsensor 38. The optical sensor 38 is on the opposite side of the spargevessel glassware from the fiber optic cable 36 that emits a light source(i.e., it is spaced-apart from the fiber optic cable 36). This will bediscussed below in greater detail. The outlet of the sparge vessel at 26is in fluidic communication with a four-way X connection 134, andfurther with the eight-port valve 140 and/or the Bake Valve 156 (V6).

There are two pressure sensors 90 and 92 in the system, also referred toas “PS#1” and “PS#2,” and there is a temperature sensor 176 in thesparge vessel area. There are some “tees” that act as three-waypassages, at 130, 132, 136, and 138, and there is an “X” connection thatacts as a four-way passage at 134. Pressure sensor 90 (PS#1) is used forregulating the back pressure in the fluidic system 10. The pressuresensor 92 (PS#2) is used to maintain the appropriate flow rate throughthe fluidic system 10, as controlled by the proportional valve 100. Aswill be understood from the fluidic schematic diagrams presented herein,pressure sensor 92 is positioned at or near the output side of theproportional valve 100.

If the temperature sensor 176 is a thermocouple, as in an exemplaryembodiment, then a K-type thermocouple plug and cable can be used, asdesignated at reference numeral 180. This will allow the sparge vesselsubassembly 20 to be dismounted (and re-mounted) in the overall system10 while allowing the thermocouple to be easily disconnected and(re-connected).

On the input side of the sparge vessel is a restrictor 120 that narrowsthe inner diameter of the tubing between the tee 136 and the NeedleValve V1. The restrictor 120 also can be of many forms, but in theillustrated embodiment it comprises a length of tubing or piping thatexhibits a predetermined volume, for example a tube about 70 inches inlength with an inner diameter of about 0.015 inches.

There are two different traps 60 and 70 in the system depicted in theflow diagram 10. The trap 60 is an “analytic trap” which can act as acondensate trap or an adsorbent trap, while the trap 70 is generallyused as a secondary adsorbent trap.

The analytic trap 60 has inlets and outlets at three places: at 62, itis connected to the eight-port valve at its port 145; at 66, it isconnected to the Dry Purge Valve 152; and at 64, it is also connected tothe eight-port valve at its port 144. The secondary trap 70 is connectedat 72 to the eight-port valve at its port 142, and at 74 it is connectedto the eight-port valve at its port 143. The analytic trap 60 has a “topportion” at 68 that can be used to receive additional carrier gas in aparticular mode of operation, as discussed below in greater detail.

The eight-port valve 140 has eight different inlet and outlet ports, andthe definitions (or uses) of these ports can be altered, depending uponthe direction or destination of gas flow through those ports. Thesevarious ports are designated 141-148. The port 147 is connected to theGC output at 82, while the port 148 is ultimately connected to the GCinput at 84. There is a heater 86 in the transfer line between theoutlet passageway 88 from the eight-port valve 140 and the inletpassageway 84 to the GC instrument 80. This allows the gaseous samplesbeing sent to the GC to remain at an elevated temperature for analyticalpurposes.

Various other passageways in the system 10 are indicated on FIG. 1A.FIG. 1 also depicts two controllers, including a heater controller 170and a proportional valve controller 110. The proportional valvecontroller 110 receives a pressure signal from the pressure sensor 90,in which the pressure signal at 104 travels to the proportional valvecontroller 110. The controller 110 outputs a signal along the pathway108 to the proportional valve itself at 100. The valve controller 110also receives a second pressure sensor signal from the sensor 92 along apathway 106. These pressure signals are used for the proper control ofthe proportional valve 100 for the various modes of operation that willbe described below in the flow charts.

The heater controller 170 receives a temperature signal from atemperature sensor 176 that is placed within the sparge vessel on itssample portion at 28. This arrangement is better viewed on FIG. 11. Theheater controller 170 has output signals that control a fan (or blower)172 and a set of resistance heating elements at 174. In one form of thepresent invention, the resistance heating elements 174 are constructedas multiple coils of resistive wire, which act as a source of thermalenergy.

In general, the heater controller 170 will be used to raise thetemperature of the sparge vessel sample portion 28 when it is time toextract VOCs from the sample. When this occurs, the heater controller170 will generally use proportional-integral-differential (P-I-D)control operating principles to increase or decrease the speed of thefan. Moreover, P-I-D-type control principles will generally also be usedto control the amount of current flowing through the resistive heatingelements 174.

Both the fan speed and the percentage of duty cycle of current sent tothe resistive heating elements 174 can be independently controlled, sothat full heat, or zero (0) heat, or any percentage in between (withinthe resolution of the controller) can be obtained at any particularinstant of time. In addition, at the end of the sample extractionprocess, and after the end of a bake cycle, the blower 172 can be run at“full speed” with the heating elements 174 turned OFF, thereby quicklycooling the sample portion 28 of the sparge vessel 20. By use ofconvection heating and cooling, the present invention allows for notonly precise control for heating the sparge vessel, but also for veryquick cooling, which is something that has not been achieved in priorsystems that simply use either radiation or conductive thermal transfer(for increasing the sparge vessel temperature, not to decrease it).

In an alternative mode of the present invention, the output percentageof the fan speed and the output percentage of the current for theresistive heating elements 174 can be controlled in a manner in whichthe numeric value of one of these outputs is related to the numericvalue of the other output (instead of each being independent of theother). For example, if the fan speed output in percent is called “F”and the heating element current output in percent is called “I”, thenthese two output values could be related in an “additive inverse”relationship, such that F+I=100%. In this example, if the fan speed (F)is at 10%, then the current (I) would be at 90%; or if F is 20% then Iis 80%, and so on. In this manner, the heating system controller 170will be able to vary the overall thermal energy transfer to the spargevessel by controlling either F (or I) using a P-I-D algorithm, and theopposite variable I (or F) will automatically have its value calculatedusing a linear equation (such as F+I=100%). In this example, the higherthe current (I), the greater the heat transfer to the sparge vessel; thehigher the fan speed (F), the greater the cooling of the sparge vessel(both because the current would be less, and also the faster the airflow, the greater the cooling effect will likely be). Of course, if F is0% and I is 100%, then there would be virtually no convective air flowto the sparge vessel, so this would not truly provide the maximumheating effect (although the blower motor might not be able to actuallystop rotating instantaneously). On the other hand, if F is 100% and I is0%, then this would provide the maximum cooling effect.

In another alternative mode of the present invention, the “additiveinverse” relationship could include an “offset” value, such that F+Idoes not equal 100%, but instead it will equal 110%, or 120%, or perhapseven 200%. For example, if F+I=200%, then the fan and current wouldalways be “pegged” at 100% output each, for maximum heating capability.This, of course, would not allow the P-I-D controller 170 to operate inits usual fashion, so a more realistic approach would be F+I=120%, orF+I=130%. In the example where F+I=120%, if F is 50%, then I is 70%; andif F is 20%, then I is 100%. The offset value could even be a negativenumber, such that F+I=80% or 90%, for example, although this probablywould be “wasting” some heating system capacity.

The P-I-D controller 170 could typically calculate the desired current(for example) several times per second, and then vary the signal valuefor 1 accordingly. Then a very small portion of the controller'sprocessing power would easily be able to calculate the appropriate valuefor F. In this manner the output values for both F and I will bemodified several times per second, using a single P-I-D controlalgorithm. However, if it is desired to not quickly and repeatedlymodify the fan motor speed many times over a typical bake cycle (e.g.,for mechanical reasons), then the P-I-D controller can be used todirectly control the fan speed (F) at a less frequent rate, and thevalue for 1 will be automatically modified at the same (less frequent)rate.

It will be understood that any realistic offset value could be used forthe F+I equation, and still be within the principles of the presentinvention. A small positive offset value will likely be preferred (sothat F+I is equal to 110% or 120%), but this really depends upon (a) howmuch heating capacity is provided by the resistive heating elements 174and (b) how much air flow capacity is provided by the fan (or blower)172, for a given sparge vessel system design. It will also be understoodthat the variables F and I can be related by a different type ofequation; or that each can be independently controlled by its own P-I-Dalgorithm (as noted above). Moreover, during the cooling mode after abake cycle, any control equation in which F+I is equal to a numbergreater than 100% would be suspended; in other words, to achieve maximumcooling, the current I should be held at 0%, regardless of the fan speed(which would typically be run at 100% during cooling mode).

In FIG. 1A, the eight-port valve is in “Position A,” the Needle Valve151 (V1) is turned OFF, while the Dry Purge Valve 152 (V2) is turned ON.This allows the Purge Mode A to occur, in which helium gas is sentthrough the proportional valve 100, Needle Valve 151, Dry Purge Valve152, and into the sparge vessel inlet at 22. The VOCs that are extractedleave the sparge vessel at its outlet 26 and travel to the eight-portvalve at its port 141. These gases continue to the secondary trap 70,through the eight-port valve at ports 143 and 144, and then to theanalytic trap 60. The gases that escape the traps continue through thepassageway 62 back to the eight-port valve at its ports 145 and 146,through the de-energized Bake Valve 156 and through the de-energizedVent Valve 153, where these gases are vented at the vent 102. At thistime, the gas chromatograph 80 can be controlled to inject gases at 82through the eight-port valve ports 147 and 148, and then back to the GCat 84. This GC gas flow may not be required, but is available in thePurge Mode A, if desired.

As noted above, if the sample that is being purged begins to foam, andif the foaming is unattended, the sample could come into contact withinternal pathway components and thereby contaminate the entire system.The sample is typically either an aqueous or a solid sample matrix, andis housed in the sealed sparge vessel (in the sample portion). The inletor “purge” gas is swept through the concentrated chemical sample at acontrolled flow rate, to extract the VOCs from that sample.

By use of the sensing subassembly 34 as a foam sensor, the system 10 candetect if foaming begins to occur. The sparge vessel contains theenlarged area, also referred to as a “foam bubble” 32, which will tendto catch the foam and break it up before exiting the sparge vessel. Foamsensor 34 is placed above (e.g., higher in elevation than) the foambubble 32, and if the foam reaches that point, then the system is aboutto encounter a problem. FIG. 1B shows an alternative Purge Mode(referred to as “Purge Mode B”) that shows how the present invention canaddress the foaming problem.

If the chemical sample is not exhibiting foaming, then the flow path ofthe helium gases does not change. However, if the chemical sampleexhibits foaming to an extent that the foam sensor is triggered, it willelectrically control the Needle Valve 151 and cause it to turn on. Thischanges the flow path of the helium gases so that they travel throughthe passageways 42 and 24 to the top portion of the other side of thesparge vessel. This effectively re-routes (or “re-directs”) the purgedgas to the second inlet at 24 to allow the sampling procedure tocontinue without aborting the sampling procedure itself. Except for thisre-routing, the rest of the flow diagram of FIG. 1B is the same as thatof FIG. 1A.

The VOCs of interest remain in the analytic traps 60 and 70, and afterthe extraction process has been completed (during a desorbtion step),those retained VOCs will be removed from the analytic absorbent trap andtransferred to the GC 80. This occurs during other modes of operation,to be discussed below, and involves switching the eight-port valve toits “Position B.” In Purge Mode B, the eight-port valve 140 remains inits Position A, the Needle Valve 151 is turned ON, the Dry Flush Valveremains ON, and the Vent Valve 153 remains ON.

Referring now to FIG. 2, the system 10 is configured for either theStandby Mode or the Dry Purge Mode of operation. The Standby mode is thefirst mode encountered when initially turning on the purge and trapanalyzer instrument 10. This is the step 200, at the beginning of theflow chart on FIG. 6. This Standby mode happens to have the same type offluidic flow movement as in the “Dry Purge” mode, which is encounteredat step 280 on FIG. 8.

During the Dry Purge mode (or Standby mode) the gas pressure source(such as helium or nitrogen) flows gas through the proportional valve100 (PV1) according to a “Dry Purge Flow” setpoint control program. Thegas flow then is directed to the needle valve 151, which is turned OFFso the flow is then directed to the Dry Purge valve 152. This valve isalso turned OFF, and the gas flow is directed along passageway 66 to thetop of the analytic trap at 68. The gas flows through the trap 60, andthen out the passageway 62 to the eight-port valve at its port 145,leaving its port 146 so the gas flow then travels to the Bake Valve 156.The gas continues to travel to the Vent Valve 153, which is de-energizedand the gas flows out its normally open port and to the vent 102. Thiswould typically be a relatively low pressure gas flow, and the Dry Purgepressure setpoint can be set by the user, but will have a defaultpressure setpoint value in the control program. The gas flow controlvalve 100 (PV1) is adjustable (as determined by the pressure controller110), and it controls the gas pressure in the trap 60 prior to thedesorbtion step.

The gas flow from the GC instrument 80 is also allowed to flow throughits outlet 82, and then through the ports 147 and 148 of the eight-portvalve 140. This gas flow then travels through the passageway 88, heater86, and the inlet passageway 84 of the GC instrument 80. Again, this canbe a relatively low pressure flow, as desired by the user. Since this isalso the configuration of the Standby Mode, the flow rates discussedabove can be either higher or lower depending upon the pressures usedand controlled by the proportional valve 100, or at the outlet of the GCinstrument 80, depending upon the user's setpoint pressure preferencesfor the Standby mode versus the Dry Purge mode.

Referring now to FIG. 3, the system 10 is illustrated in a “Desorb” Modeof operation, which is short for “Desorbtion.” In FIG. 3, the mode ofoperation is also referred to as a “No Split” Mode, which will bedescribed in greater detail below. In the Desorb Mode, the eight-portvalve is switched to its Position B, so that the compounds of interestthat have been trapped in the analytic trap 60 can be sent to the GC 80.In this mode, the injection gas from the GC at its outlet 82 flowsthrough the eight-port valve at its ports 147 and 145, and continues tothe “bottom” of the trap 60 at the passageway 62. The compound orcompounds of interest are removed from the trap while it is being heatedto a predetermined temperature during this gas flow of the DesorbtionMode. These compounds are directed through a passageway 64 and to theeight-port valve through ports 144 and 148, and to the outlet 88. Afterpassing through the heater 86, the compounds of interest are directed tothe inlet of the GC at 84. This is a fairly standard mode of operationfor analyzer instruments of the type sold by various companies,including EST Analytic, the assignee of the present invention.

In FIG. 3, the method parameter is desorbtion pressure control. Thepressure sensor 90 sends a signal along 104 to the proportional valvecontroller 110. At a predetermined pressure, the system vent 102 can beclosed by use of the Vent Valve 153. This action will seal off thefluidic pathway at the predetermined setpoint value prior to thedesorbtion step, if desired. This is an alternative desorbtion mode,which is illustrated on FIG. 4.

In FIG. 4, the alternative desorbtion mode is referred to as the DesorbMode “With Split.” The proportional valve controller 110 receives asignal at 106 from the other pressure sensor 92. This signal is used tocontrol the proportional valve 100 for controlling the desorbtion gasflow rate that is in fluidic communication with the analytic trap 60,which is also in communication with the GC 80. A feedback loop is thuscreated by using the pressure signal from the sensor 92 to control theproportional valve 100, for controlling the gas flow rate which willeventually reach the analytic trap 60 and the GC 80.

In FIG. 4, the gas flow travels from the proportional valve 100 throughthe Needle Valve 151, Dry Purge Valve 152, and into a passageway 66 thatreaches the analytic trap 60 at its “top portion” 68. This effectivelyadds an additional gas stream to the desorbtion pathway, and is referredto in the present invention as the “Split Flow” arrangement. In essence,the trap 60 has a “first chamber” that is coupled to a fluidic inletthat receives the gases from the GC 80, through the passageway 62. This“first chamber” had previously received a concentrated chemical samplefrom the sparge vessel 20 during a previous step of the analysisprocedure. As the gases from the GC pass through the first chamber, itacts to remove at least one predetermined substance of interest fromsaid concentrated chemical sample, and thus an “extracted sample” gasflow is created that passes from the first chamber.

Trap 60 also contains a “second chamber” in essence, which is the topportion 68. The second chamber is coupled to the first chamber, suchthat the extracted sample gas flow passes from the first chamber intothe second chamber. This second chamber 68 is also coupled to a fluidicinlet that is in fluidic communication with the passageway 66, and thusback to the PV1 valve 100, and finally back to the input gas source viathe passageway 50. Therefore, the second chamber receives both theextracted sample gas flow from the first chamber and the inlet gasesfrom the PV1 valve 100.

In this manner, the additional gas flow through the top portion 68 ofthe analytic trap 60 combines with the GC's own helium gas flow, whichthe GC provided through the outlet 82 through the eight-port valve 140and into the bottom of the trap at 62. Thus, both of these gas flowstravel through the pathways 62 and 66, and thereby exit the analytictrap through the passageway 64, back through the eight-port valve 140and back to the GC at its inlet 84. This is a way of obtaining a greatervolume of gas samples for the GC, and occurs without drawing water fromthe analytic trap 60, due to the gas flow through the passageway 66. Thegreater gas volume allows the GC to achieve a greater sensitivity whenmeasuring for the chemical composition of interest in the sample gasesreceived at its inlet 84.

This operating mode is also referred to as the “Desorb Column Pressure”Mode. The pressure control valve 100 (PV1) can maintain or increase thepressure in the trap 60 so that it operates at a predetermined splitflow pressure setpoint. Once the system pressure at pressure sensor 92reaches a predetermined setpoint, the proportional valve 100 (PV1) canbe turned OFF (to its 0% output), and this will stop the flow throughthe passageway 66 entering the analytic trap 60. Once that occurs, the“Split Flow” Mode will no longer continue.

It will be understood that the flow control valve 100 (PV1) does notnecessarily need to have a proportional flow capability to perform inthis “Split Flow” mode of operation. In other words, as an alternativeembodiment, the control valve 100 could be replaced by a standard“ON-OFF” gas valve (e.g., a solenoid valve) that permits either zeroflow (0%) or full flow (100%), and no other “in between” flow ratevalue, while nevertheless performing in the Split Flow mode of operationthat is described above in conjunction with FIG. 4. The enhancedperformance of the Split Flow mode is primarily due to the additionalgas flow that travels to the GC 80, via the gas that travels through theflow control valve 100 from the Helium input device at 50. The amount ofgas flow through the passageway 66 could be regulated (if necessary) byanother method than use of a proportional valve for PV1.

Referring now to FIG. 5, the system 10 is illustrated as it would beconfigured for a “Bake Mode” (or “bake procedure”). During this BakeMode, the temperature of the sparge vessel is controlled by use of theheater controller 170, which controls the fan/blower 172 and alsocontrols the magnitude of current through the resistive heating elements174. Because of the fan's air flow, and using ductwork to direct thisair flow, the thermal energy from the heating elements 174 is therebyforced by thermal convection to the sample portion 28 of the spargevessel 20. This will tend to clean the surfaces of the sparge vessel,while the bake temperature can be precisely controlled, generally usinga P-I-D algorithm for controlling the sparge vessel heater temperature.The actual temperature is detected by a temperature sensor 176, whichtypically can be a thermocouple, or some other type of metallictransducer, such as a resistance temperature detector made of platinum(also referred to as a “RTD”).

During the Bake Mode, the Dry Purge Valve 152, and the Backflush Valve154 are turned ON, along with the Bake Valve 156. The Vent Valve 153 isOFF, which allows gas flow through it normally-open port. The eight-portvalve is set to its Position A. The proportional valve 100 is nowcontrolled to a “bake flow” setpoint by the PV controller 110.

Referring now to FIG. 11, the sparge vessel area is depicted as beingmounted on a mounting plate 510, in which the sparge vessel 20 has itsfoam sensor (i.e., the sensing subassembly 34) surrounding the outletportion 26 of the sparge vessel. As discussed above, the foam sensor hasa fiber optic cable that directs light through the sparge vessel, and anoptical sensor on the opposite side of the sparge vessel outlet 26 toreceive that light if no foaming is occurring. If foaming occurs to asufficient extent, then the foam bubbles will tend to interfere with thereception of the light on the optical sensor side of the detector; a“high level” of liquid at sensor 34 will also interfere with thereception of light. By use of this arrangement, the foam sensor 34 actsas both an overfill sensor and a foam detection sensor, using a singleoptical sensing device 38.

The foam sensor 34 includes the termination end of the fiber optic cable36, which emits electromagnetic energy at a predetermined wavelength,such as a visible light wavelength or an infrared wavelength. The fiberoptic cable acts as an optical waveguide, and it has an opposite“receiving” end that is optically coupled to a light source, such as alight emitting diode (LED) or a laser diode, for example. The systemcontroller (e.g., the “heater controller” 170) includes a signalgenerator that can adjust the magnitude of the optical energy that isemitted by the light source, if desired. The signal generator also cancause the light source to emit pulses of electromagnetic energy, ifdesired. The optical sensor 38 essentially can be any form of transducerthat responds to electromagnetic energy (e.g., photons), and the mostcommon forms used are a photodiode or a phototransistor, withappropriate biasing electrical components. This includes photovoltaiccells, for example.

The heater subassembly is generally depicted by the reference numeral500 on FIG. 11. The blower (or fan) is at reference numeral 172, and iscontained inside a ducting or ventilating conduit area by ducting 522,with certain ventilation slots 524. The heating elements 174 arecontained within a secondary ducting arrangement at 532. When the fan isturning, air will be forced through the ducting 522 and into the ductingarea 532 where the heating elements 174 are positioned. In this manner,the heating elements 174 act as a radiant heater within the ducting area532, and the moving air thus heated will then pass through a slot 512 inthe mounting plate 510 and be directed to the sample portion 28 of thesparge vessel 20. This effectively heats the sparge vessel sampleportion 28 by thermal convection. This ducting arrangement can also bereferred to as a “ductwork subassembly.”

It will be understood that electrical conductors or “leads” will benecessary for the fan 172 and the resistive heating elements 174. Theseelectrical leads are not illustrated in FIG. 11, for purposes ofclarity. The same is true for the fiber optic cables that extend intothe foam sensor 34; there will be such cables extending through themounting plate 510 to the right (on FIG. 11), but those cables are notdepicted on FIG. 11 for the purposes of clarity. The electrical lead tothe temperature sensor is depicted at reference numeral 540 on FIG. 11,and the extension to the temperature sensor itself is at 176.

At the end of the bake cycle, it is desirable to quickly cool the spargevessel. The present invention does so by blowing cool air via the fan172, while the heating elements 174 are de-energized. This will quicklycool the sparge vessel 20, and it is possible to cool the sparge vesselfrom a bake temperature setpoint to a purge temperature setpoint in lessthan ninety seconds, thereby enabling the system 10 to quickly begin anew sampling cycle.

Before a desorption step begins, the purge and trap system of thepresent invention may also be configured to pressurize the “dead volume”involving the eight-port valve 140 and the input to the GC instrument80. This dead volume includes the passageway 62, at the “bottom” of theanalytic trap 60, and sometimes may include the passageway 64 betweenthe trap 60 and the port 144 of the eight-port valve 140.

As noted above, in conventional purge and trap systems, the dead volumeis not pressurized by the purge and trap system before the analyzer trapis heated, and before the GC's carrier gas begins to flow through thesepassageways 62 and 64. When the GC instrument's pressurized carrier gasis “switched” into the passageway 62 by the eight-port valve (throughthe analyzer trap 60), a sudden pressure increase occurs which can causethe problems discussed above.

The present invention uses a pressure control valve (e.g., theproportional valve 100) to create a pressure in the passageway 62 at the“bottom” of the trap 60, preferably before the trap begins to be heatedand before the desorbtion step begins. This pressure is referred toherein as the “desorbtion pressure control,” or “DPC” pressure. The DPCpressure is controlled by the PV controller 110, and uses a pressuresensor 92 to provide a feedback control signal that indicates the actualsystem pressure in real time at the output side of the pressure controlvalve 100. As the DPC pressure is built up, the PV controller 110 willdecrease the gas flow through the pressure control valve 100, so thatthe desired DPC pressure is substantially maintained. If the pressurecontrol valve 100 is a proportional valve (or some other type ofvariable output pressure or variable flow valve), then the PV controllerwill be able to directly control the system pressure based on thefeedback signal from pressure sensor 92. If the gas flow rateessentially falls to zero while maintained the DPC pressure, then thesystem will be “deadheaded,” and the pressure everywhere in the systempassageways will be substantially equal to the pressure at the sensor92, since there will be no pressure losses at “no flow.”

The DPC pressure in the system at the trap 60 may be built up at the endof a dry purge mode, for example, by closing the vent 102 (e.g., byusing the vent valve 153), and then ramping the pressure from near zeroto the desired DPC pressure. By building a pressure in the system at thetrap 60, the passageway at 62 will not experience a sudden pressureincrease when the eight-port valve 140 cycles (changes state) from itsposition A to position B. This provides an improvement in the transferrate and in the analytical resolution of the extracted VOCs; also itreduces or eliminates moisture from being transferred to the GCinstrument 80 when sampling an aqueous sample matrix, which wouldotherwise affect the analytical resolution and detected recovery of theextracted VOCs.

The DPC pressure setpoint can be selected by a user, by entering data ona user interface that communicates commands to the system controller.This is discussed in greater detail below, in the discussion of the flowcharts. The software executed by the system controller will typicallycontain a default pressure value for the DPC pressure setpoint.

It will be understood that the desorption pressure control feature ofthe present invention can be used with either the “split mode”desorption cycle of FIG. 4, or the “normal mode” desorption cycle ofFIG. 3.

Discussion of Flow Charts

Referring now to FIG. 6, the beginning of a flow chart showing some ofthe important steps in an automatic controller routine are illustrated.Starting with a “Standby” mode at 200 (which is displayed on a computermonitor screen), a step 202 turns ON the sample heater fan 172 and alsobegins the standby flow of helium gases. Along with the fan (or blower)172, the heat controller 170 also will energize the electrical heatingelements at 174. This will begin to raise the temperature of any samplenow in the sparge vessel 20.

A decision step 204 is executed next, and it determines if all of the“loaded” temperature zones are currently at their setpoints. Thesetemperature zones are described at step 206 on the flow chart of FIG. 6.As can be seen in the illustrated example of the present invention,there are twelve different heating temperature zones, and each one canhave a different temperature setpoint value and a different temperaturetolerance if desired. If all of the temperature zones are not at theirsetpoint (within their correct tolerance), then the logic flow travelsfrom the NO output back to the top of decision step 204 until all of thezones are within their predetermined tolerances of the setpointtemperatures. After that occurs, the logic flow arrives at a “PurgeReady” mode at a step 210, which displays this status on the computermonitor.

A step 212 now turns on the “ready” indicator light (so the user can seethat the Purge Ready mode has occurred), and starts a time delay for a“first pass” of delay in the purge cycle. The “waiting” cycle begins acountdown until it reaches zero (0), at a step 212. A decision step 214now determines whether or not there has been an overfill within thesparge vessel. If not, then a step 230 begins the process of stepping tothe purge mode. Step 230 determines if the Purge Start input has beenactivated, and if so, the controller will turn off the Purge Readyindicator message. As the system is waiting to “Step to Purge,” it iswaiting for an input. This could be a manual input at the operatordisplay control panel, or it could be an automatic input based upon anexternal signal received as an input by the controller. A decision step232 now determines whether or not the sample heater is still on, and ifnot, the logic flow travels to a step 252 that turns on the “Purge”indicator message, and the system now has entered the “Purge” mode at250.

Referring back to decision step 214, if an overfill condition exists,then a step 220 will display the overfill icon on the computer screen,and will write to an Error Log, in which the entry will state that theoverfill was active in a run status. A decision step 222 now determineswhether or not the system should continue toward the purge mode. This isan input that the user controls, and if the user enters a NO input, thenthe logic flow is briefly directed to an “Overfill” mode display messageat 224, and the logic flow is directed back to the Standby mode at 200.On the other hand, if the user wishes to continue, then the logic flowis directed out the YES output from step 222, and this logic flowtravels to a letter “A” that is further directed to FIG. 8, and will bediscussed below.

At decision step 232, if the sample heater is still ON, the indicatinglight #3 will begin flashing at a step 234. The logic flow is thendirected to a step 238 (see FIG. 7) in which the status is checked tosee if the pre-purge time is greater than zero (0), and also the purgeflow valve 100 (which is the proportional valve PV1) will now becontrolled using the pre-purge flow setpoint value. This is alsoreferred to as the “Pre-Purge” mode at 236 on FIG. 7, which displaysthis status on the computer monitor.

Once the conditions at step 238 have been satisfied, the logic flow isdirected to a step 242 in which the preheat temperature is set to be thesample heater program temperature, and the preheat time is set equal tozero (0). This is also referred to as the “Pre-Heat” mode at 240 whichis displayed. The logic flow is now directed to step 252, in which thesystem enters the “Purge” mode 250, which is displayed.

Once the Purge mode has been entered, a step 254 begins the purge flowprogram. (This is Purge Mode “A,” as illustrated on FIG. 1A. The purgeflow valve 100 (proportional valve PV1) is set to control using thepurge flow control setpoint value. The Dry Purge Valve is also turned ON(this is valve V2 at 152). A decision step 256 now determines whether ornot the “foam sensor option” has been selected by the user. If YES, thena decision step 260 determines whether or not the foam sensor input isnow active. If not, then the logic flow is directed back to the purgeflow program at step 254. On the other hand, if the foam sensor input isactive, the logic flow is directed to a decision step 262 thatdetermines whether or not the foam detect selection option has beenplaced into the “STOP” mode or the “CONTINUE” mode. If the STOP mode hasbeen selected (by the user), then a step 264 aborts this sample run, andthe logic flow goes back to the Standby mode, and a message is displayed(on the system monitor) at a step 266 that foam has been detected andthat the sparge vessel should be cleaned.

At step 262, if the CONTINUE selection has been entered, then a step 268stops the purge cycle, and sets the purge flow valve 100 (PV1) to avalue of zero (0), which stops the purge flow. The Dry Purge Valve 152(V2) is turned OFF, and an entry is written to the Run Log that foam hasbeen detected, in the CONTINUE mode. The logic flow is then directed toa decision step 290 on FIG. 8, through the letter “G,” which will bediscussed below.

If the foam sensor option has not been selected by the user at decisionstep 256, the logic flow is directed to a step 270 in which the purgetime is set to zero (0), the Dry Purge Valve 152 (V2) is turned OFF, andthe Needle Valve 151 (V1) is also turned OFF. A step 272 now turns thesample heater OFF, and the logic flow is then directed to a Dry Purgemode through the letter “E” and to FIG. 8 (discussed below).

Referring now to FIG. 8, the logic flow through letter “E” is directedto a step 282 which begins the “Dry Purge” mode at 280, which isdisplayed. An indicator light is also turned ON to inform the user thatthe Dry Purge mode has been entered. The purge flow valve 100 (PV1) isnow set to run using the dry purge flow program setpoint.

Each of the traps 60 and 70 have their own heater and their own heatersetpoint. The dry purge trap heater controller 170 is now set to the drypurge trap setpoint, which is an entry that can be controlled by theuser (but also has a default, or suggested setpoint temperature). Thetrap pressure can be controlled by the pressure control valve 100 (PV1)prior to thermal heating of the adsorbent trap 60.

The logic flow is now directed to a step 284 that sets the dry purgetimer to zero (0), and turns off the dry purge indicator light. Anotherindicator light is turned ON, and the purge flow is set to zero (0).Once the Dry Purge mode has been completed, the logic flow is directedto a step 212 that waits until the GC 80 (the gas chromatograph) isready. This is the “Desorb Ready” mode at 210, which is displayed.

The logic flow entering FIG. 8 through letter “G” is directed to adecision step 290 in which it is determined if the foam detect systemusing the Needle Valve 151 (V1) needs to activate to run in the PurgeMode B, illustrated in FIG. 1B. If the answer is NO, then the logic flowis directed to the Desorb Ready step at 312. On the other hand, if theanswer is YES, then a decision step 292 determines whether or not thefoam sensor input is active or not. If it is not active, then the NeedleValve 151 (V1) is turned ON at a step 296. The purge flow program isresumed (in Mode B). On the other hand, if the foam sensor input is notfalse (meaning the foam sensor is active), then a step 294 causes thesystem to wait until the foam sensor input reads false (which meansthere is no foam at this time). A Wait step 294 essentially loops backto the beginning of the decision step 292, where the foam sensor inputis again inspected.

From step 296, a decision step 300 determines if the foam detectalgorithm has now entered its second loop. If the answer is NO, then theDry Purge cycle is completed at step 284, and the Desorb Ready mode isentered at 312. If the second loop is active at step 300, then a step302 stops the purge, and sets the purge flow valve 100 (PV1) to zero(0), turns the Dry Purge Valve 152 (V2) OFF, turns the Needle Valve 151(V1) OFF, and writes an entry to the Run Log. This entry will state thatfoam was detected at the “Needle Valve Purge Continue” mode (i.e., PurgeMode B on FIG. 1B). When this occurs, the purge gas is thereby re-routed(during the foam detect second loop).

The logic flow now is directed to the Desorb Ready mode at step 312. Thelogic flow from letter “A” also is directed to the Desorb Ready step312. From this step, the logic flow is directed to FIG. 9 through theletter “D.” The “Desorb Ready” status is displayed at step 310.

On FIG. 9, the system is now waiting for the gas chromatograph to become“Ready.” This is the Desorb Ready mode 310, which is displayed. Whilethe system is at the Desorb Ready Mode 310, at the logic step 314 thesystem is waiting for an input. Again, this input could be a manualentry by person at the operator display control panel of the systemcontroller, or it could be an external signal received as an input bythe controller. At a step 312, the Desorb Ready status is also madeapparent to the user by turning on an indicator light.

From step 312, a decision step 320 now determines whether or not the gaschromatograph input indicates that it is ready, and if not a Wait step322 loops the logic flow back to the beginning of decision step 320.Once the GC is actually ready and the input is received at step 320,then the logic flow travels out the YES output to a decision step 324.The purpose of decision step 324 is to detect whether a foamingcondition or an overfill occurred earlier for this sample; again thefoam detector is now inspected. If the answer is YES, then the logicflow is directed to a step 354 that delays the GC start for two secondsand turns on an indicator light for the Inject mode.

If the logic flow reaches step 354, then the concentrated sample in thetrap will be discarded and not sent to the GC 80. The desorb timer isstarted, and a delay of two seconds is imposed before turning on theDrain Valve (V5) output. The logic flow is then directed to a decisionstep 360 where it is determined whether the automatic drain function hasbeen selected.

Back at decision step 324, if there is no detection of an overfill, thenthe logic flow is directed to a decision step 332 that determines if thedesorbtion column pressure is now ON. This is the “DCP” mode 330, whichis displayed. If the answer is YES, then a step 334 controls the purgeflow valve 100 (PV1) to the desorbtion column pressure setpoint. Theproportional valve 100 is set to a “Desorbtion Column PressureSetpoint.” Once the setpoint pressure is reached, the purge flow is setto zero (0), using proportional valve PV1, and then no appreciable flowwill be output from the valve 100. A step 336 now writes to the log amessage that the column pressure balance injection setpoint pressure isat a particular (current) control setpoint in PSI, and also writes theactual pressure in PSI units to the log. The logic flow is now directedto a step 342.

If the desorbtion column pressure mode was turned OFF at step 332, thenthe logic flow is also directed to step 342. The system is now enteringthe “Desorb Pre-Heat” mode 340, which is displayed. In the DesorbPre-Heat mode at step 342, the trap heater is set to the Desorb Pre-Heatsetpoint. An indicator light is now flashed to inform the user of thisstatus. A step 352 now sets the analytic trap 60 to the Desorb setpoint,and it sets the eight-port valve 140 to its “Position B.” (See the flowdiagram of FIG. 3 for this configuration.)

The trap 60 is now instructed to use its heater at a desorb temperaturesetpoint by the first instruction in step 352. After eight-port valve140 is set to Position B, an electrical signal is sent to the GC 80instructing it to start its run, since the purge and trap system hasjust injected a sample. The gas chromatograph 80 starts outputting itsgas supply, and the indicator light that was flashing in step 342 is nowturned ON continuously, to indicate that the GC injection has begun.

The last instruction in step 352 is a signal to an external device (suchas an autosampler) to actuate its drain, and this signal is alsoreferred to as a “drain signal” being sent from the purge and trapsystem. A desorb timer is started, and its countdown “timeout” to adrain output is two seconds (in this embodiment). This is the Desorbmode 350 (which is displayed on the User Controller), and in an optionalmode of the present invention, the pressure control valve 100 (PV1) canbe set to a “Split Flow” rate, which will be discussed in greater detailbelow. This is the mode that was discussed above in reference to FIG. 4,and is an enhancement provided by the present invention. In this“Desorbtion Split Flow Mode,” the proportional valve 100 is now set tooperate at the “Desorbtion Split Flow Rate,” and the flow passagewayswill be used as depicted on FIG. 4.

The logic flow has now reached a decision step 360, where it isdetermined if an automatic drain function should be performed, and ifnot, a step 366 sets the desorb timer to zero (0) and moves theeight-port valve 140 back to Position A (which is the positionillustrated in FIG. 2).

If the automatic drain function is to be used, then a step 362 controlsthe purge flow valve 100 (PV1) so that it controls from the purge flowsetpoint. The Drain Valve (V5) is turned ON, the Backflush Valve 154(V4) is turned ON, and the Dry Purge Valve 152 (V2) is turned ON. A step364 determines if the drain time has reached the active desorb timeparameter, and also determines if the desorb time has reached zero (0).If so, the Drain Valve (V5), Backflush Valve (V4), and Dry Purge Valve(V2), are all turned OFF. The logic flow is now directed to step 366where the desorb timer is set to zero (0) and the eight-port valve isset to Position A. The logic flow is now directed to the “Bake” modethrough the letter “H.”

Referring now to FIG. 10, the system is about to reach the Bake mode. Astep 370 can be activated such that the user may manually command thesystem to enter the Bake mode (“Step to Bake”), by a user input. Adecision step 372 will determine whether or not the system should stepto the Bake mode with the drain activated. If the answer is NO, then thelogic flow is directed to step 382 and the Bake indicator light isturned ON. This is now the “Bake” mode 380, which is displayed on theuser monitor screen.

In the Bake mode, the sparge vessel 20 receives a rinsing liquid, andalso receives a “bake gas,” which will tend to clean the glassware inpreparation of receiving a new chemical sample at the sparge vessel. Thesystem controller provides electrical signals to cause these steps tooccur. In addition, the rinsing liquid can then be removed from thesparge vessel, again under the control of the system controller and itselectrical signals.

If the Bake mode with drain is to be used, the logic flow is directedfrom step 372 to a step 374 in which the purge flow valve 100 (PV1) isset to control from the bake flow setpoint. The Drain Valve (V5) isturned ON, the Backflush Valve 154 (V4) is turned ON, and the Dry PurgeValve 152 (V2) is turned ON. As the Bake mode is running, a step 376 nowdetermines if the drain time has reached the active desorb timeparameter, and also will set the desorb time to zero once that has beenaccomplished. The Drain Valve (V5), Backflush Valve (V4), and Dry PurgeValve (V2) are all turned OFF. The logic flow is now directed to a step384. This step 384 is also encountered from step 382.

At step 384, many things occur: the bake mode begins by setting up aprogrammable bake flow, and a Start Bake timer is initiated to be set toa bake time (in minutes) that can be controlled by the user (there is asuggested or default value). The purge flow valve 100 (PV1) is set tocontrol from the bake flow setpoint. The Backflush Valve 154 (V4) isturned ON, the Vent Valve 153 (V3) is turned ON, the Bake Valve 156 (V6)is turned ON, and the Dry Purge Valve 152 (V2) is turned ON. Also, step384 determines if the bake gas bypass mode is turned ON, and if so, flowto the sparge vessel is bypassed. This is accomplished by keeping theDry Purge Valve 152 (V2) turned OFF.

The bottom instruction of step 384 can use a “Bake Gas Bypass Mode,” ifdesired by the user. In that situation, the needle valve 151 (V1) isturned ON, and the Dry Purge valve 152 (V2) is turned OFF. This willre-direct the gas flow so that it travels along the passageway 42 and 24to the upper portion of the “sample portion” of the sparge vessel, andthen out the sparge vessel's outlet passageway 26. This will effectivelybypass the sparge vessel during the bake mode, if desired. This is analternative mode, and this bypass gas flow mode is not illustrated onFIG. 5.

A decision step 390 now determines if the sample heater is turned ON. Ifnot, the logic flow is directed to a step 394. If so, a step 392controls the sample heater to a bake temperature program, and the sampleheater is turned ON. This includes both the blower (or fan) 172 and theresistive heating elements 174. The percentage output for the resistivewire heater could be all the way from 100% duty cycle all the way downto 0% duty cycle, if desired. This can be adjusted using binary numbers;with an 8-bit number, the resolution would be one part in 256, which isabout one-quarter % precision. Of course, if a greater resolution isdesired, then the controller can use larger binary numbers to controlthe duty cycle, such as 10-bit or 12-bit numbers (providing one part in1024 for 1/10% precision, or one part in 4096 for 1/40% precision,respectively).

The blower fan speed can be controlled at a fairly wide range, dependingupon the type of motor and blower fan being used. In one mode of thepresent invention, this range can be from full duty cycle (100%) down aslow as 20% duty cycle. Of course, the blower motor can be completelyturned off, if desired, depending upon whether or not the purge and trapsystem is going to be not used for fairly long periods of time. Inaddition, the blower fan's control signal can be varied in the range0-100% if desired, even if the physical fan cannot slow all the way downto zero RPM, without actually turning it off. The blower fan can also becontrolled using binary numbers of a predetermined resolution, such aswith 8-bit, 10-bit, or 12-bit numbers. It will be understood that analogcontrol techniques could be used instead of digital control techniques,if desired, in the present invention.

The first instruction at step 394 is for the trap 60, which is set toits particular bake temperature setpoint. The second instruction is forthe other trap 70 (also referred to as the “pre-trap”), which is set toits particular bake temperature setpoint. Thus, at step 394 the trapheater is turned ON to the trap bake setpoint program. Also thetemperature zone H8 is turned ON to the pre-trap bake setpoint. A step396 determines if the bake time has reached zero (0), which means thatthe bake timer has timed out, and if so, a step 398 controls theanalytic trap 60 temperature to the “Trap Ready” setpoint, and turns thesample heater 174 to its “Ready” setpoint value.

An optional feature of the present invention is to use multiple Bakecycles before proceeding to the next sampling procedure step, or beforereceiving the next chemical sample at the sparge vessel. This featurecan be automatically implemented by a user selection, in which the userwould enter (in advance) the number of Bake cycles that the purge andtrap concentrator system 10 will undergo. Of course, the number ofselected Bake cycles could be only one, which is the conventional methodthat has been used in the past. On the other hand, the present inventionallows for a greater amount of “cleaning” of the glassware by providingadditional Bake cycles, and this can be done automatically.

The present invention also provides greater flexibility in controllingthe sparge vessel temperature during Bake cycles (or Bake “steps”). Forexample, an “initial” temperature setpoint is provided for selection bythe user, which become the process control variable at the beginning ofthe Bake step. Then the temperature setpoint can be increased, and thistemperature rise over time can be controlled as a “ramp” function, ifdesired; that is, the user can select a numeric ramp value in units ofdegrees vs. time. The initial temperature setpoint can be held for aselectable amount of time by the user (a “hold time” setpoint), beforethe temperature increase begins to take effect. Furthermore, the maximumBake step temperature is selectable by the user, and if desired, a“final” sparge vessel temperature setpoint can be selected by the user,in which the final temperature may be different than the maximum Bakestep temperature. Thus the sparge vessel temperature will follow aprogrammable temperature profile that begins with the controlled initialtemperature (for a predetermined time period), then the controlledtemperature rise (at a predetermined rate of increase), until reachingthe maximum Bake temperature, which will be the control variable formost of the remainder of the Bake step; finally the controlled finalBake temperature will be used as the process control variable, at theterminal portion of the Bake step.

In step 398, the sample heater 174 is turned off, while the fan (orblower) 172 is turned on to its full 100% duty cycle. This is the“cooling mode” for the sparge vessel, in which the electricallycontrolled device (i.e., the fan) is also used to move air for removingthermal energy from the sparge vessel. The other instructions in thisstep 398 are to instruct the trap 60 and 70 to turn their heaterscompletely off, so as to also be in the “cooling mode.” For example, thesparge vessel 20 could be heated to 85 degrees C. as the final spargevessel temperature for a Bake step, and it is then quickly cooled toambient temperature, within a fairly tight tolerance (such as ±5 degreesC.). For a given sampling application, the present invention can bedesigned so that the time to cool the sparge vessel does not inhibit thenormal sample analysis cycle time for a purge and trap concentratorsystem.

As the sparge vessel 20 is cooled, the system is ready to go back to thestandby mode (which is at step 200 on FIG. 6). This completes the cyclefor a particular group of samples. On FIG. 10, The term “H8 (mort)” is areference to a moisture reduction trap, as is the term “H7 (mort).” Suchmoisture reduction traps can be used as the traps 60 and 70 on FIG. 1A,for example.

It will be understood that the heater controller 170 and theproportional valve (PV1) controller 110 could be two separate controldevices or they could be routines that are resident on a single processcontrol computer. Such a process control computer could be a generalpurpose PC, using Microsoft WINDOWS as a graphic user interface, forexample, or using UNIX or LINIX. A general purpose PC would preferablyhave a display monitor to show various equipment statuses, and/or aseries of indicator lights (such as LED's) to show the status of thevarious modes used in the present invention. Any controller wouldtypically include a processing circuit (e.g., a microprocessor or alogic state machine) and a memory circuit (e.g., RAM, ROM, EEPROM,etc.). In addition, it will be understood that the proportional valvecontroller 110 could operate using either analog or digital controltechniques. If a digital controller is used, the valve control signalcould be of 8-bit resolution, for example, which would provide aprecision of one part in 256. A greater precision may well be desirable,and the valve control signal therefore use larger binary numbers, suchas 10-bit numbers for one part in 1024 precision, or 12-bit numbers forone part in 4096 precision. Even greater precision is possible by usinglarger binary numbers for the control algorithms.

If a microprocessor or microcontroller (i.e., a “digital controller”) isused as the proportional valve controller 110, then the binary signalsthat are calculated by the digital controller would typically be arelatively low voltage, low current electrical signal, such as a 0-5 VDC(or 4-20 mA) analog output signal from the digital controller. Thisassumes that the digital controller has some type of on-board Digital toAnalog Converter (DAC). Otherwise, the digital controller could output abinary signal (either serial or parallel) to a separate DAC module, andthat DAC module would output the low voltage, low current signal. Such alow power 0-5 VDC signal could not directly drive the proportional valve(PV1) 100, and so a driver module would typically be used to convert thelow power signal to a more substantial (or “high power”) signal. Anexemplary driver module for this purpose is a Series B5950 proportionaldriver, sold by Canfield Connector of Youngstown, Ohio.

If a microprocessor or microcontroller (i.e., a “digital controller”) isused as the heater controller 170, then the binary signals that arecalculated by the digital controller would typically be a relatively lowvoltage, low current electrical signal, such as a 0-5 VDC analog outputsignal from the digital controller. This assumes that the digitalcontroller has some type of on-board Digital to Analog Converter (DAC).Otherwise, the digital controller could output a binary signal (eitherserial or parallel) to a separate DAC module, and that DAC module wouldoutput the low voltage, low current signal. Such a low power 0-5 VDCsignal could not directly drive the motor for the blower 172, and so adriver module would again typically be used to convert the low powersignal to a more substantial (or “high power”) signal. An exemplarydriver module for this purpose is a model AX10415 analog output module,sold by AXIOM Technology Co., Ltd. in Taiwan; another exemplary drivermodule for this purpose is a model M3000 motion controller, sold bySystem Semiconductor, Inc., of Marlborough, Conn.

Two tables are provided below that summarize the use of the six solenoidvalves and of the four-way valve 140 (i.e., the eight-port valve) forthe various modes illustrated in the fluidic schematic diagrams anddiscussed above with respect to the logic flow chart. The first tableshows the name of the system mode and the corresponding fluidicschematic drawing, and also shows the type of logic control setpointsthat the proportional valve 100 will be using for the various operatingmodes. The second table again shows a listing of the mode in theleft-hand column, and then lists the various modes or states of thesolenoid valves, including the eight-port valve 140 and the six solenoidvalves 151-156 (V1-V6). These tables are provided as follows:

TABLE #1 PURGE FLOW Mode Drawing PVI Purge A FIG. 1A Purge Flow Purge BFIG. 1B Purge Flow Standby/Dry Purge FIG. 2 Dry Purge Flow Desorb - NoSplit FIG. 3 Desorb with Drain (PV = 0) Desorb - With Split FIG. 4Desorb Column Pressure Bake FIG. 5 Bake Flow BGB FIG. 5* BGB Flow

TABLE #2 NEEDLE DRY VENT FLUSH DRAIN BAKE Mode 8-port V1 V2 V3 V4 V5 V6Purge A A OFF ON OFF OFF OFF OFF Purge B A ON ON OFF OFF OFF OFFStandby/ A OFF OFF OFF OFF OFF OFF Dry Purge Desorb - B ON ON ON ON ONOFF No Split Desorb - B OFF OFF ON OFF OFF OFF With Split Bake A OFF ONOFF ON OFF ON BGB A ON OFF OFF ON OFF ON

The judicious use of the solenoid valves and the four-way valve 140control the flow passageways for carrier gas, noble or inert gas throughthe proportional valve 100 (PV1), and the sample gases that run from thesparge vessel 20. These solenoid valves and the four-way valve alsocontrol the pathways of the gases that run through the traps, as well aswhat gases get vented (and to where) in a particular mode. It will beunderstood that the exact configurations depicted in the fluidicschematic diagrams of FIGS. 1A-5 could have certain alterations whilestill achieving the same effect, all without departing from theprinciples of the present invention.

It will be understood that the logical operations described in relationto the flow charts of FIGS. 6-10 can be implemented using sequentiallogic, such as by using microprocessor technology, or using a logicstate machine, or perhaps by discrete logic; it even could beimplemented using parallel processors. One preferred embodiment may usea microprocessor or microcontroller to execute software instructionsthat are stored in memory cells within an ASIC. In fact, the entiremicroprocessor, along with RAM and executable ROM, may be containedwithin a single ASIC, in one mode of the present invention. Of course,other types of circuitry could be used to implement these logicaloperations depicted in the drawings without departing from theprinciples of the present invention.

It will be further understood that the precise logical operationsdepicted in the flow charts of FIGS. 6-10, and discussed above, could besomewhat modified to perform similar, although not exact, functionswithout departing from the principles of the present invention. Theexact nature of some of the decision steps and other commands in theseflow charts are directed toward specific future models of chemicalanalyzer systems (those involving EST analyzers, for example) andcertainly similar, but somewhat different, steps would be taken for usewith other models or brands of chemical analyzer systems in manyinstances, with the overall inventive results being the same.

All documents cited in the Background of the Invention and in theDetailed Description of the Invention are, in relevant part,incorporated herein by reference; the citation of any document is not tobe construed as an admission that it is prior art with respect to thepresent invention.

The foregoing description of a preferred embodiment of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed, and the present invention may be further modified within thespirit and scope of this disclosure. Any examples described orillustrated herein are intended as non-limiting examples, and manymodifications or variations of the examples, or of the preferredembodiment(s), are possible in light of the above teachings, withoutdeparting from the spirit and scope of the present invention. Theembodiment(s) was chosen and described in order to illustrate theprinciples of the invention and its practical application to therebyenable one of ordinary skill in the art to utilize the invention invarious embodiments and with various modifications as are suited toparticular uses contemplated. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1. A method for operating a purge and trap concentrator system, saidmethod comprising: (a) providing a system controller, a gas source thatsupplies a first gas flow, a plurality of fluidic control devices and aplurality of fluidic passages which fluidically connect said pluralityof fluidic control devices, an analytic trap, a first fluidic inlet thatis in communication with an external analyzer instrument, and a firstfluidic outlet that is in communication with said external analyzerinstrument; (b) receiving a second gas flow from said external analyzerinstrument, through said first fluidic inlet; (c) placing a concentratedchemical sample into a first chamber of said analytic trap, directingsaid second gas flow into a first end of said first chamber and removingat least one predetermined substance from said concentrated chemicalsample, thereby creating an extracted sample gas flow that is directedto a second end of said first chamber; and (d) receiving, at a secondchamber of said analytic trap, said extracted sample gas flow from saidfirst chamber; receiving, at a second inlet of said second chamber ofsaid analytic trap, said first gas flow from said gas source; andcombining said first gas flow and said extracted sample gas flow at saidsecond chamber and to create an enhanced gas flow that is directedthrough a second outlet of said second chamber and further to said firstfluidic outlet, and to said external analyzer instrument, therebyproviding a larger overall enhanced gas flow that now becomes availablefor analysis by said external analyzer instrument.
 2. The method ofclaim 1, further comprising: providing a gas flow control valve that iscontrolled by a signal from said system controller, said gas flowcontrol valve being positioned between said gas source and said secondinlet of the second chamber, and when commanded by said signal, passesat least a portion of said first gas flow therethrough.
 3. The method ofclaim 2, wherein said gas flow control valve comprises a variableposition valve that exhibits a low flow mode in which its output gasflow is at a minimum amount, a full flow mode in which its output gasflow is at a maximum amount, and a proportional flow mode in which itsoutput gas flow is at a value between said minimum amount and saidmaximum amount, under control of said signal.
 4. The method of claim 3,wherein: (a) said low flow mode is a percentage of fluid flow that issubstantially 0% of said maximum amount of fluid flow, (b) said fullflow mode is a percentage of fluid flow that is substantially 100% ofsaid maximum amount of fluid flow, and (c) said proportional flow modeis a percentage of fluid flow that varies between 0% and 100% of saidmaximum amount of fluid flow, through said variable position valve. 5.The method of claim 4, further comprising the step of controlling saidvariable position valve using an analog signal.
 6. The method of claim4, further comprising the step of controlling said variable positionvalve using a binary signal of multiple digits, thereby providing alarge number of discrete possible positions.
 7. The method of claim 6,wherein said binary signal is one of: (a) 8-bit resolution, therebyproviding 256 different possible positions between 0% flow and 100%flow, inclusive; (b) 10-bit resolution, thereby providing 1024 differentpossible positions between 0% flow and 100% flow, inclusive; and (c)12-bit resolution, thereby providing 4096 different possible positionsbetween 0% flow and 100% flow, inclusive.